Asset tracking systems in previous systems relied upon the detection of an asset tracking device by a radio frequency detection device. For example, the asset would pass by the detection device and the detection device would by some detection means detect a “tag” or other identifier attached to the asset. The asset tracking system would know the location of the asset because the system would have knowledge of the location of the detection device. An example of a radio frequency detection means may include engaging a radio frequency identifying (RFID) tag or the like attached to the asset. Like a barcode, the RFID tag may provide information about the asset.
The known asset tracking systems employing radio frequency detection means usually require the detection means to actively engage the tag attached to the asset being tracked. Other examples include more complex asset tracking tags that may communicate with devices within the location in order to update information related to the tag or its location, and report the location of an asset through wireless radio frequency communication. The transmission of position updates and data reporting causes the asset tracking tag to continuously operate in a high power consumption state.
Locations of radio devices (e.g., tags) in an area served by a network of RF beacons having known locations can be estimated by a variety of means in the prior art. Received signal strength of signals transmitted by a tag, a RF beacon, or both may be measured by a tag and/or the RF beacon, and used as a proxy for node-to-tag distance (assuming that all nodes transmit signals of equal strength): the farther away the transmitting tag/node, the lower the received signal strength. Present systems require the transmission of the RSS values as well as additional information for the determination of the location of an asset tag. However, this continuous processing of and transmission of data consumes power and adds traffic to the RF communication channels.